Flow Preferences with Load Balancing

Getting noticed

Flow Preferences with Load Balancing



Wondering how is going to react traffic with this configuration, with load balancing enabled:




1- Will sourced traffic always go out WAN 2


2- Will all other traffic be load balanced, or will it follow the 2nd rule of Flow preferences and always go out on WAN 1.


3- Are Flow preferences working the same way as layer 3 firewall rules (up to bottom, first hit is applied)


What has precedence over what



Do Flow preferences override the Enabled Load Balancing




Kind of a big deal

Flow Preferences

By default (without load balancing), internet-bound traffic will flow out of the MX's primary uplink. The MX can also be configured to send traffic out of a specific interface based on the traffic type (policy-based routing), or based on the link quality of each uplink (performance-based routing). Flow preferences can be configured to define which uplink a given flow should use. Flow preferences will also supersede load balancing decisions. 

Internet Traffic

Flow preferences for internet-bound traffic can be configured to force traffic over a specific uplink based on its source and/or destination. These preferences can be used if a specific uplink should be designated for a particular type of traffic, such as traffic bound for a cloud-hosted service. 

Note: ICMP traffic is not subject to traffic shaping rules. As a result, Flow Preference will have no impact on ICMP traffic.

Well, seems I read the doc too fast


yeah this sentence says a lot : Flow preferences will also supersede load balancing decisions. 


For point # 3, still haven't found anything regarding how are applied the rules

If they are not applied this way : up to bottom, first hit is applied, then rule #2 would supersede rule #1


Kind of a big deal

Well, I think that for internet traffic this doesn't make any sense, but if you think about it logically, the order will always be from top to bottom.

But, in this configuration, you must define whether the traffic from a given source to a specific destination must use WAN 1 or WAN 2.

Did you get It?

By the way, If you want to know about route priority:


Route Priority

Each type of route configured on the MX has a specific priority in comparison with other types of routes. The priority is as follows:

  1. Directly Connected
  2. Client VPN
  3. Static Routes
  4. AutoVPN Routes
  5. Non-Meraki VPN Peers
  6. BGP learned Routes
  7. NAT*

Yes, as in the screenshot


Because our customer asked us few weeks ago to enable load balancing, then comes back to us today with these new needs. must go out on WAN 2

All other traffic must go out on WAN 1


So I think the real need in the end will be to disable load balance, and add only 1 rule : out WAN 2 




would Load Balance Enabled + the 2 rules applied manage the traffic the same way ??



Kind of a big deal

If in fact, it is not a necessity to have balancing enabled I would go with the first option, disable load balancing and "force" the specific source to go out through WAN 2.

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